Process for producing lubricating oil by hydrogen treatment

ABSTRACT

A PROCESS FOR HYDROTREATING CRUDE LUBRICATING OIL STOCKS TO PRODUCE LUBRICATING OILS WITH DESIRED YIELD-VISCOSITY DISTRIBUTION AND VISCOSITY INDEX BY RECYCLING A SELECTED FRACTION TO THE HYDROTREATING OPERATING.

Feb. 9, 1971 Q BRYSQN ETAL 3,562,149

PROCESS FOR PRODUCING LUBRICATING OIL BY HYDROGEN TREATMENT 'Filed Aug. 19, 1969 I l I I l I I I l I I I I I I l I I l I I i I I l i I I I I l l I I I l I I II I! v u Qh hwwxpwk Qh u Q n n m W n NW WWW. n w w "Jam V N m VW" 0 A M X n \N m u u 6 N\ a n n 3 V D 0 a e Q v W n/mes;

41/1 L4A 0 C B/PISO/V JAMES R Ml/APA) HARRY 6'. EMU/PEA United States Patent Ofice 3,562,149 Patented Feb. 9, 1971 US. Cl. 208-143 5 Claims ABSTRACT OF THE DISCLOSURE A process for hydrotreating crude lubricating oil stocks to produce lubricating oils with desired yield-viscosity distribution and viscosity index by recycling 2. selected fraction to the hydrotreating operation.

This application is a continuation-in-part of our application Ser. No. 601,587, filed Dec. 14, 1966 and now abandoned.

It has previously been suggested in the art to produce lubricating oils by subjecting hydrocarbon materials boiling above about 650 F. to various types of hydrogen treatment. Thus, for example, it has been suggested to subject higher boiling hydrocarbons particularly hydrocarbons containing components boiling above about 900 or 1000 F. to extremely severe hydrogen treatment, generally termed hydrocracking. In a hydrocracking process there is extensive and somewhat random severing of carbon to carbon bonds as well as removal of contaminants such as sulfur, oxygen and nitrogen with a substantial overall reduction in molecular weight and boiling point of the treated material. Usually, hydrocracking processes produce substantially large quantities of materials boiling below about 650 F. and relatively lesser quantities of materials boiling in the lubricating oil range, to the extent that at times the production of a lubricating oil is merely incidental to the production of gasoline and furnace oil.

Two other hydrogen treatment processes which are most often associated with the production of lubricating oils are hydrofinishing and hydrotreating. Both of these hydrogen treatment techniques are substantially less severe than a hydrocracking operation. Of these two hydrogen treating operations, hydrofinishing and hydrotreating, hydrofinishing is the less severe treatment. Thus, for example, in hydrofinishing the catalyst employed usually does not possess cracking activity and as a result usually no hydrocracking is effected during the course of hydrofinishing. Hydrofinishing, however, does effect a reduction of sulfur, oxygen and nitrogen compounds in the treated material and, depending upon the relative severity of the treatment within the overall mild treating conditions of hydrofinishing, there may be no saturation of aromatic compounds or substantial saturation of aromatic compounds.

As distinguished from hydrofinishing, hydrotreating is a somewhat more severe processing technique, although substantially less severe than hydrocracking. Thus, in hydrotreating the catalyst employed must possess cracking activity. Generally, hydrotreating efiects substantial molecular rearrangement as compared to hydrofinishing but does not effect the extensive and somewhat random breakdown of molecules effected in hydrocracking. Usually, the type of catalyst employed in hydrotreating has a particular type of activity known as ring scissiori. Normally in a hydrotreating process there is substantially complete saturation of aromatics and the reaction is believed to follow the course of converting condensed aromatics to condensed naphthenes followed by the selective cracking of the condensed naphthenes to form single ring alkyl-naphthenes. Thus, polynuclear cyclic compounds are attacked and the rings are opened, while mononuclear cyclic compounds are not substantially affected. The alkyl side chains formed by opening the rings in polynuclear compounds are not further reacted to sever the alkyl side chains. Hydrotreating is also effective for the isomerization of parafiins. Thus, hydrotreating reduces the quantity of aromatics and polynuclear cyclic compounds as well as the quantity of normal parafiins, thereby reducing the bromine number of the treated material and increasing its viscosity index. A typical employment of a hydrotreating process is to convert cylinder stocks or bright stocks to high viscosity index neutral oils.

The particular operation involved in the process of our invention is hydrotreating as distinguished from hydrofinishing and hydrocracking. The materials normally charged to a hydrotreating operation can be termed crude lubricating oil stocks and are generally obtained from crude petroleum by distillation so as to provide a material boiling at least above about 650 F. Depending upon the crude petroleum from which the 650 F.-}- materials are obtained such materials may be subjected to solvent extraction prior to being charged to the hydrotreating process. When the material obtained by distillation is a residual fraction it may, depending upon the crude source, be subjected to deasphalting such as, for example, propane deasphalting, prior to being charged to the hydrotreating process. The product materials from the hydrotreating process may be fractionated and blended with each other to produce desired lubricating oil products. In many instances, depending upon the end use of the lubricating oils, such materials may be subjected to finishing operations such as acid and clay contacting or the hydrofinishing treatment described above.

When operating a commercial hydrotreating operation, a refiner usually attempts to produce the various grades of lubricating oils having the desired viscosity index (VI) and the desired viscosities in approximately the quantities required by the marketing situation through adjustment of the charge stock composition. Even in the most ideal situation, however, a refiner is limited by the type and composition of the crude lubricating oil stock available to him and the extent to which the composition of the material charged can be varied. Generally, the requirement both in quantity and quality of the highest boiling of the desired fractions exerts the greatest infiuence on the selection of charge stock composition and reaction conditions. Thus, for example, the quantity and quality of bright stock desired at a particular refinery is the predominant factor in determining the composition of the crude lubricating oil stock charged and the conditions employed which in turn determine the quantity and quality of the distillate or neutral lubricating oils produced. In a great many instances the result is the production of excessively large quantities of certain lighter lubricating oils or the production of completely undesired lubricating oil fractions.

Another typical problem is the production of lower viscosity lubricating oil fractions whose VI is undesirably low. In this connection it is pointed out that, while at comparatively high viscosity levels there is usually some increase in VI with a decrease in viscosity, at lower viscosity levels there is usually a decrease in VI (at times a sharp decrease) with a decrease in viscosity. This phenomenon of decreasing VI with decreasing viscosity is in some instances noticed with lubricating oil fractions hav ing a viscosity as high as about 200 SUS at 100 F. Generally, this phenomenon can be seen almost universally when dealing with lubricating oil fractions having viscosities at 100 F. of less than about 150 SUS. In any event, this phenomenon exists with the lower viscosity fractions of all lubricating oils produced by hydrotreating even though the viscosity level at which it first becomes noticeable may vary from about 200 SUS at 100 F. to 150 SUS at 100 F. or lower. It is primarily to the solution of the problems created by this phenomenon to which our invention is directed and as employed herein the term lower viscosity is meant to encompass those lighter lubricating oil fractions exhibiting such penomenon.

While some of these problems can be remedied by blending high viscosity and/or high VI fractions with lower viscosity and/or lower VI fractions such techniques still result in the production of various lubricating oil fractions in excess of the amount demanded by the market. Storage of such presently undesired products, sale of such fractions at distressed prices or conversion to or blending with less profitable products is obviously not desirable. It has previously been found, however, that further processing of undesired lubricating oil fractions or portions thereof, while generally being effective to increase the VI of the fraction further treated, obtains a VI increase at the expense of substantial losses in viscosity together with substantial quantitative losses to less desirable lower boiling materials.

In accordance with the process of our invention the undesired lubricating oil fractions or portions thereof which have a viscosity greater than the viscosity of the lowest boiling components of the lubricating oil product from a hydrotreating operation are recycled to extinction in the hydrotreatment step. Unexpectedly, we have found that when operating the hydrotreating step and recycle operation in accordance with our invention there is an overall increase in materials of desired viscosity and an increase in the VI of the product without an excessive loss to lower boiling, non-lubricating oil materials. These advantageous results of our invention occur through not only a general increase in the VI of the total product but by a significant increase in the VI of the lighter, lower viscosity, lower boiling fractions of the overall lubricating oil spectrum. Thus, rather than having a sharp decrease in VI from the heavier, higher viscosity lubricating oil fractions to the lighter, lower viscosity lubricating oil fractions the process of our invention is eflFectve to provide products wherein the VI of the front end of the spectrum or lighter, lower viscosity fractions more closely approaches the VI of the heavier lubricating oil fractions.

The crude lubricating oil stocks suitable for treatment in accordance with the process of our invention can be any of the types well known in the art, which stocks boil generally above the furnace oil range and include materials boiling in the gas-oil or heavy gas-oil range and above. Thus, for example, such crude lubricating oil stocks usually boil predominantly above about 650 F. and include stocks ranging from distillates to residues obtained from vacuum or atmospheric towers. Generally, distillates are considered to encompass stocks boiling in the range from about 650 up to about 1000 or 1100 F. While residues can be defined as comprising the most difiiculty vaporizable materials which generally cannot be distilled without effecting decomposition or cracking of the stock. Illustrative of suitable crude lubricating oil stocks are distillate materials boiling above about 650 F. obtained from Ordovician or Kuwait crude oils as well as deasphalted oils, cylinder stocks and low carbon residue atmospheric or vacuum residua. We have found that particularly suitable feed stocks for employment in our invention can be in the nature of a so-called long residuum, which stock can be obtained as the bottoms fraction from an atmospheric tower and will usually boil from about 750 F. upward. When treating a residual material, whether obtained from an atmospheric or vacuum distillation, we have found that it is usually advantageous to subject such stock to a deasphalting treatment such as treatment with a light parafiinic solvent, particularly propane. It must be pointed out, however, that it may not be necessary to subject all residual fractions to a deasphalting treatment before charging them to the process of our invention. Thus, for example, residual fractions obtained from a Pennsylvania type crude oil are in many instances of sufficiently low asphalt content that no deasphalting is necessary. The stocks charged to the process of our invention can also include materials which have been treated for the reduction of aromatic content such as, for example, the rafiinates from solvent extraction processes including the raffinate from a Duo-Sol treatment.

In conducting the process of our invention we employ a temperature in the range from about 600 to about 900 F. and preferably from about 700 to about 800 F., a total pressure from about 2500 to about 5000 p.s.i.g. and preferably from about 2800 to about 3500 p.s.i.g., a hydrogen partial pressure of about 2500 p.s.i. or greater and preferably from about 2600 to about 3300 p.s.i., a liquid hourly space velocity (LHSV) from about 0.1 to about 10.0 and preferably from about 0.5 to about 3.0 volumes of total charge stock per hour per volume of catalyst and a total hydrogen feed rate to the reactor from about 1000 to about 20,000 standard cubic feet of hydrogen per barrel of charge stock (s.c.f./b.) and preferably from about 2000 to about 6000 s.c.f./b. It is not necessary that pure hydrogen gas be charged to the process of our invention and hydrogen-containing gaseous streams available from other processes in a refinery can be employed, such as, for example, the hydrogen stream from a reforming process. Generally, however, any such hydrogen-containing stream should be comprised of at least about 60 percent hydrogen and preferably at least about percent hydrogen. As mentioned above, it is necessary to recycle a stream to the process of our invention and the recycle rate employed can vary from about 10 to about 500 or 600 percent by volume of recycle based upon fresh feed. Preferably, however, the recycle rate employed will be at least about 50 percent by volume based on fresh feed.

The catalyst employed in our invention is a two-component catalyst comprising a hydrogenating component composited with a carrier or base having particular requirements, which will be described more fully below. The hydrogenating component can include any of the well known Group VI and Group VIII hydrogenating metals, and their oxides or sulfides either alone or in combination. The carrier or base of the catalyst required in our process must possess some cracking activity. Materials of this nature are known to the art. It is not necessary, however, to employ carriers having extremely high cracking activi ties and we have found that carriers having cracking activities on the Kellogg scale of less than about 30 and even less than about 20 are satisfactory. Illustrative of such a carrier is alumina. Thus, for example, suitable catalysts include combinations of nickel and tungsten, preferably sulfided nickel and tungsten, on an alumina carrier as well as a combination of nickel, cobalt and molybdenum on an alumina carrier. The catalysts employed in the process of our invention can also be promoted with a small amount of a halogen, such as, for example, from about 0.2 to about 10 percent of the total weight of the catalyst. Preferably the halogen content of the catalyst is in the range from about 1.0 percent to about 5.0 percent by weight. We have found that it is most advantageous to employ fluorine as the halogen promoter, particularly when employing a nickel-tungsten catalyst.

Although the metals content of the catalyst used in our process can vary from about to about 50 percent by weight, we prefer to employ catalysts containing at least about percent by weight total metals. A particularly preferred catalyst form employed in the process of our invention comprises a combination of nickel and tungsten on alumina wherein the nickel and tungsten comprises at least about percent by weight of the total catalyst and preferably at least about 30 percent by weight with the nickel and tungsten present in an atomic ratio of nickel to tungsten varying from about 2.2521 to about 6:1 and preferably from about 2.5:1 to about 5.0:1.

The catalyst employed in our invention can be prepared utilizing any of the techniques for the preparation of multicomponent catalysts well known in the art. Thus, for example, we can prepare our catalyst by impregnating a calcined alumina employing a solution of the salts of the desired metals. When it is desired to incorporate a halogen promoter into the catalyst, the halogen can also be included in the impregnating solution. Depending upon the particular metals to be employed in the catalyst and the quantity of metal desired in the catalyst the impregnation can be conducted in one or a plurality of steps in accordance with techniques well known in the art.

The hydrotreating operation employing the conditions and catalyst described above in accordance with our invention is effective to produce a substantial quantity on a non-dewaxed basis, at least about 50 percent by volume based on fresh crude lubricating oil stock, of a hydrotreating lubricating oil boiling above about 650 F. Preferably, at least about 75 percent by volume of nondewaxed lubricating oil is produced. From the hydrotreated lubricating oil is selected at least one fraction which has a viscosity greater than the viscosity of the lowest boiling components of the lubricating oil and boils above about 725 F. At least a portion of the fraction so selected is recycled to the hydrotreatment step. In any particular refinery operation the specific fraction or frac tions selected is determined by the market demand for various lubricating oils which the refinery is supplying. Thus, for example, the fraction selected can be the highest boiling components of the hydrotreated lubricating oil or it can be some intermediate fraction, i.e. neither the highest or lowest boiling components nor the most or least viscous components, such as a fraction boiling above about 750 F. or 800 F. up to about 850 F. or 900 F. If the particular selected fraction or fractions represents a completely undesired lubricating oil or oils, the entire fraction or fractions can then be recycled to the hydrotreating step. If, on the other hand, the situation is such that merely an excessive quantity of a particular fraction or fractions is being produced then only the excess of the fraction or fractions would be recycled in accordance with our invention.

The result of recycling the selected fraction or fractions in accordance with our invention is the production of an increased quantity of lower viscosity hydrotreated lubricating oil product boiling above about 650 F. with a concomitant increase in VI of the desired product, while minimizing the production of lower boiling non-lubricat ing oil materials. Thus, in accordance with our invention, the overall production of material boiling below about 650 F., on a on-dewaxed basis, is less than about 50 percent by volume based on the fresh crude lubricating oil and preferably is less than about 40 percent by volume. On the other hand, however, the overall production of desired hydrotreated lubricating oil, on a nondewaxed basis, will be above about 70 percent by volume based on the fresh crude lubricating oil and usually will be closer to about percent by volume. On a dewaxed basis these yields are equivalent to the production of about 60 percent by volume or more of desired hydrotreated lubricating oil based on fresh crude lubricating oil.

The particular recycle ratio employed, it will be understood, will be determined by the quantity of undesired fractions produced initially and the market requirements. Generally, however, a recycle ratio of at least about 10 percent by volume based on fresh feed should be employed. We have found that recycles ratios up to about 300 percent by volume are satisfactory in most instances and recycle ratios as high as 500 or 600 percent by volume can at times be employed advantageously.

The particular fraction or fractions to be recycled to the hydrotreating operation of our invention can be obtained from the hydrotreater efiluent stream either before or after such stream has been dewaxed. We prefer, however, to recycle non-dewaxed materials to the hydrotreat ing operation in order to eifect additional conversion of some of the waxy constituents to desirable lubricating oils. Recycle of a fraction subsequent to dewaxing is quite satisfactory and, if production of wax is a desired operation in a particular refinery, permits recovery of a greater quantity of wax.

Reference is now made to the attached drawing which shows a schematic flow diagram illustrating the basic process of our invention and variations thereof.

The fresh feed stock comprising a crude lubricating oil stock boiling above about 650 F. is passed by means of line 10 into reactor 12. Hydrogen flowing at a rate of about 5000 s.c.f./b. of fresh feed stock is introduced into line 10 by means of line 14. In hydrotreating reactor 12 the fresh feed of line 10 together with hydrogen of line 14 are contacted with a dual component catalyst comprising a hydrogenation component composited with a cracking base having an activity of less than about 30. The temperature, pressure and space velocity maintained in reactor 12 are within the ranges described previously. The effluent from hydrotreating reactor 12 is passed by means of line 16 to fractionator 18. Hydrogen and gaseous hydrocarbons are removed overhead from fractionator 18 by means of line 20 while the furnace oil and lighter liquid products are removed by means of line 22 and passed to product recovery means, not shown. Lines 24, 26 and 28 are provided for the removal of lubricating oil fractions boiling above 650 F. with the lightest lubricating oil being removed by means of line 24 and passed to a solvent dewaxing operation represented by block 30. Dewaxed light lubricating oil product is removed from dewaxing operation 30 by means of line 32 and passed to product recovery means, not shown. Slack wax is removed from the solvent dewaxing operation as indicated by line 33. Line 26 in the drawing is representative of the removal from fractionator 18 of an intermediate lubricating oil fraction boiling above about 725 F i.e. a fraction having a viscosity greater than and boiling above the lighter fraction removed by means of line 24. Line 28 is representative of the removal from fractionator 18, of a heavy lubricating oil fraction, i.e. a lubricating oil comprising the highest boiling and most viscous components of the total lubricating oil.

The flow scheme in the attached drawing illustrates an arrangement which permits alternative operations in accordance with our invention which might become desir able as dictated by variations in demand for different types of lubricating oil. Thus, in one type of operation valve 34 in line 26 would be opened, while valve 36 in line 38, which line connects with line 26, would be closed, thereby passing the intermediate fraction of line 26 directly to the dewaxing operation 30 to produce a dewaxed intermediate lubricating oil fraction which can be removed from the dewaxing operation 30 and passed to product storage means, not shown, by means of line 40. In this type of operation valve 42 in line 44 would be closed while valve 46 in line 48 would be opened, thereby permitting the heavy, undewaxed, hydrotreated lubricating oil to be removed from fractionator 18 by means of line 28 and then passed through lines 48 and 50 back to line for recycle to hydrotreating reactor 12.

Alternatively, valve 34 in line 26 can be closed while valve 36 in line 38 is opened, thereby permitting the intermediate lubricating oil fraction of line 26 to be passed by means of lines 38 and 50 back to line 10 and then recycled to hydrotreating reactor 12. In such operation valve 46 in line 48 would be closed while valve 42 in line 44 would be opened thereby permitting the heavy lubricating oil fraction removed from fractionator 18 by means of line 28 to be passed directly through line 44 to dewaxing operation 30 so as to provide a dewaxed heavy lubricating oil fraction which is removed from dewaxing operation 30 and passed to product storage, not shown, by means of line 52.

It will be understood, of course, that valves 34, 36, 42 and 46 can also be adjusted so as to effect recycle of only a portion of either or both the intermediate fraction of line 26 and/ or the heavy fraction of line 28.

An alternate method of operation is also illustrated in the drawing. =In accordance with this variation, valves 36 and 46 are maintained in the closed position, thereby permitting all of the intermediate fraction to be passed directly from fractionator 18 to the dewaxing operation 30 by means of line 26 and all of the heavy fraction to be passed directly from fractionator 18 to dewaxing operation 30 by means of lines 28 and 44. Subsequent to the dewaxing operation 30 all or part of the dewaxed intermediate lubricating oil fraction of line 40 can be recycled as indicated by valved line 54 shown as a broken 8 quantity of wax removed from dewaxing operation 30 by means of line 33.

In order to illustrate our invention in greater detail, reference is made to the following examples.

EXAMPLE I In this example a deresined cylinder stock having an ASTM-D 1160 five percent boiling point of 940 F., a saturates content of about 66 percent by volume and an aromatics content of about 34 percent by volume, inspection data for which are shown in Table I below, was employed as the charge stock to a series of runs. In the first run of this series a single-pass operation was employed and in the subsequent two runs recycle operation employing dilferent recycle ratios was employed. The catalyst employed in all three runs was a sulfided nickel-tungsten on alumina catalyst which had been promoted with two percent fluorine. The total metals content was percent by weight based on the total catalyst comprised of 20 percent nickel and 20 percent tungsten. The carrier was comprised substantially entirely of a commercially available alumina having an activity on the Kellogg scale of 16.1 (AI=18).

In each run, the efiluent from the hydrotreater was fractionated so as to obtain a gas fraction, a C furnace oil fraction having a nominal end point of 600 F. (actual percent point varying from about 570 to 590 F.), a light lubricating oil fraction (actual 5 percent point varying from about 665 to 685 F.) and a heavy, high viscosity fraction boiling above about 1000 F. The light lubricating oil fraction was dewaxed employing a 50/50 MEK-toluene mixture in a 4/1 solvent to oil ratio and a 15 F. filter temperature. The heavy lubricating oil fraction was recycled to the hydrotreating step in the two recycle runs without dewaxing. The inspection data for the products obtained in the three runs together with the operating conditions employed are shown in Table I below.

TABLE I Type of run Hydrotreating conditions Single-pass Recycle Average catalyst temperature, F 758 759 762 Reactor pressure, p.s.i.g 3, 500 3, 500 3, 500 Space velocity, vol./hr./vol.:

'lot feed 0. 52 O. 52 0.95

Fresh feed 0. 52 0. 34 0. 28 Recycle, percent by vol. of F.F 53 240 Hz consumption, s.c.f./bbl.F.F 622 725 1, 089 Yields, percent by vol. fresh feed:

C3-C5 gas 0. 6 0. 4 0. 1

C furnace oil 16. 2 28. 5 37. 6

Waxy low viscosity lube stock. 25. 0 80. 4 74. 6

Light neutral oil 20. 8 64. 6 64. 3

Slack wax (15% oil content) 4. 2 15. 8 10. 3

Waxy high viscosity lube stoc 64. 4

Total recovery 106. 2 109.3 112. 3

Waxy Dewaxed high light Dewaxed viscosity neutral light neutral Inspections Charge lube oil oil Gravity, API 26. 8 32. 4 32. 6 35. 1 35. 8 Viscosity, SUV, sec

F a 1, 800 B 640.0 158. 8 169. 6 121.0

210 F 132. 5 81. 4 44. 9 46. 7 42. 3 Viscosity index 104 119 129 130 Pour point, F 85 0 0 0 Flash point, F 590 560 430 445 415 Sulfur, percent 0. 07 0. 05 0. 05 0. 05 0. 05 Carbon residue, rams per 0. 70 0. 07 0. 17 0. 04 0. 03 Basic nitrogen, p.p.rn 72 5 5 5 5 Color, D1500 L6. 0 L2. 0 L1. 5 L1. 0 L1. 0 Iodine number 19. 1 2. 9 6. 6 6. 7 5. 1

* Extrapolated.

line. Similarly, all or part of the dewaxed heavy lubricating oil fraction of line 52 can also be recycled in the manner represented by valved line 56, also shown as a broken line. It will be seen that both lines 54 and 56 communicate with line 10 which carries the fresh feed stock. As mentioned previously, operation in accordance with this alternative method is effective to increase the were effective to produce a light neutral oil having a viscosity index of at least ten points higher than obtained in the single-pass operation. Furthermore, it will be noted that the overall production of the desired neutral oil in the recycle run is about three times the quantity of light neutral oil obtained in the single-pass operation. Moreover, this three-fold increase in desired neutral oil is obtained with a relatively small increase in the quantity of furnace oil and lower boiling materials. It will also be noted that the light neutral oils obtained from the recycle runs in accordance with our invention are all high quality lubricating oils as indicated by their viscosity, their high viscosity index, low pour point and iodine number as well as a substantially reduced carbon residue and a somewhat lower ASTM-D 1500 color.

EXAMPLE II In this example, a steam refined cylinder stock having an ASTM-D 1160 five percent boiling point of 930 F., a saturates content of about 63 percent by volume and an aromatics content of about 37 percent by volume, inspection data for which are shown in Table II below, was employed as the charge stock to a series of hydrotreating runs employing various operating conditions. In each of the runs recycle operation in accordance with our invention was practiced. The catalyst employed in all three runs was the nickel-tungsten on alumina described in Example I. Again, as in Example I, the efiiuent from the hydrotreater was fractionated so as to obtain a gas fraction, a C -furnace oil fraction having a nominal end point of 600 F. (actual 90 percent point varying from 570 to 590 F,), a light lubricating oil fraction (actual 5 percent point varying from about 690 to 720 F.) and a heavy, high viscosity fraction boiling above about 1000 F. Also, as in Example I, the light lubricating oil fraction was dewaxed at 15 F. and the heavy fraction was recycled to the hydrotreating step. The inspection data for the products obtained in these three runs together with the operating conditions employed are shown in Table 11 below.

TABLE II Hydrotreating conditions Average catalyst temperature, F 762 762 780 Reactor pressure, p.s.i.g 3, 500 3, 500 3, 500 Space velocity, vol. lhr. Vol.1

Total feed 0. 51 1. 07 0. 52 Fresh feed 0. l9 0. 17 0. 24 Recycle, percent by vol. of F. 168 530 117 H2 consumption, s.c.f./bbl. F.F 920 1, 219 928 Yields, percent by vol. of fresh teed:

C3-C5 gas 0.4 0. 5 0.1 Ca furnace i] 27. 3 40. 9 31. 2 Waxy low viscosity lube stock 82. 6 71. 1 70. 8 Light neutral oil 64. 4 61. 3 62. 4 Slack wax (15% oil content) 18. 2 9.8 17. 4 Total recovery 110. 3 112. 5 111. 1

Dewaxed light Inspections Charge neutral oil Gravity, .API 25. 6 34. 1 35. 2 34. 1

B 3, 000 182. 2 142. 7 176. 3 182. 6 47. 3 44. 1 46. 8 103 124 128 124 Pour point, F... 50 5 5 0 Flash point, F 605 455 435 445 Sulfur, percent 0. 11 0. 05 0. 05 0. 05 Carbon residue, rams, percent. 1. 74 0. 07 0. 03 0. 06 Basic nitrogen, p.p.m 147 5 5 5 Color, D1500 D 8.0 dil. L2. 0 1. 0 L2. 0 Iodine number. 20. 5 7. 2 4. 2 4. 8

I Extrapolated.

From the data shown in Table II above, it will be seen that the process of our invention is suitable for treating an even somewhat less desirable charge stock than employed in Example I and that a wide range of temperatures as well as varying space velocities can be employed in accordance with our invention to obtain satisfactory quantitative yields of high quality lubricating oils. Thus, for example, in all of the runs shown in Table II a yield of dewaxed light neutral oil in excess of 60 percent by volume was obtained and yet the production of furnace oil and lighter material was always about 40 percent by volume or less. Examination of the inspection data for the three products indicates that the light neutral oils obtained were high quality lubricating oils having a high viscosity index and low sulfur, nitrogen and carbon residue contents. Similarly, the ASTM-D color and the iodine number of the products were satisfactorily low.

An examination and comparison of the data shown in both Tables I and II demonstrates that the products obtained from the two different feed stocks were of excellent quality as indicated by almost negligible nitrogen and sulfur contents, low carbon residues (0.03-0.07 percent), low iodine numbers (4-7) and good color (L 1.0 L 2.0). Of particular interest is a comparison of the light neutral oil products obtained from the recycle treatment of both the deresined and steam refined cylinder stocks of Examples I and II, respectively. Although the deresined cylinder stock had a substantially lower viscosity (132.5 vs. 182.6 SUS at 210 F.), a more than 50 percent lower carbon residue (0.70 percent vs. 1.74 percent) and nitrogen content (72 vs. 147 ppm.) and a better color (L 6.0 vs. D 8.0 dil.) than the steam refined stock, the yield and VI of the light neutral oils from recycle hydrotreating of the steam refined stock were quite similar to those from recycle treatment of the deresined stock. This similarity in the quality of the various products obtained is also quite suprising in light of the very large variations in reaction conditions. Such results are in sharp contrast to those usually noted in a single-pass hydrotreating operation. It will be noted, therefore, that in spite of the wide variations in quality of the two feed stocks, the range of operation temperatures from 759 to 780 F. and the percent variation in space velocities from 0.5 to 1.0, the yields of dewaxed light neutral oils ranged only from 61.3 to 64.6 percent while the VIs of such oils varied in the very narrow range from 124 to 130.

Further comparison of the data in Tables I and II indicates that when operating a recycle process in accordance with our invention, high space velocities and high recycle operation favors the conversion of wax. In both Tables I and II the yield of slack wax was about 5 to 8 percent less at 1.0 space velocity than at 0.5 space velocity. correspondingly higher yields of the C to furnace oil fractions were obtained during the 1.0 space velocity operations. Thus, it will be seen that high space velocity and high recycle rate operation lend themselves to higher yields of by-product, furnace oil and lighter products. Conversely, low space velocity and low recycle rates are preferred when high yields of by-product wax are desired.

EXAMPLE III In this example a Kuwait lubricating oil feed stock blend having the inspections shown in Table III below was employed as the charge stock to both single-pass and recycle hydrotreating operations. The catalyst employed in both the single-pass and recycle operations was the same sulfided nickel-tungsten on alumina catalyst employed in Examples I and II. As distinguished from the recycle runs demonstrated in Examples I and II the recycle operation of this example was conducted by recycling an intermediate fraction, i.e. neither the heaviest nor lightest lube oil fraction. The particular operating conditions employed as well as the yields obtained are also shown in Table III below.

TABLE III Charge stock inspections:

Gravity, API 20. 2 Viscosity, SUV 108. 4 Pour point, F 85 Flash point, F-.. 510 Sulfur, percent 3. Rams. carbon residue, percent 1. 4 Total nigroten, p.p.m.. 340 Iodine number 16. Processing conditions:

Type of run Average catalyst temperature, F 750 750 Reactor pressure, p.s.i.g 3, 000 3, 000 LHSV:

Total feed 1. 0 1. 0 Fresh feed 1. 0 0. 1, 100 1, 150

1. 2 1. 25 18. 5 25. 0 86. 9 84. 75 13. 9 13. 55 Dewaxed lube stock 73. 0 71. 2

Viscosity, Viscosity, Viscosity SUV at Viscosity SUV at index 100 1*. in ex 100 F.

Light lube 75 70 12. 8 80 70 SA 10 90 150 15. 104 150 225 neutral (recycled) 3 100 225 105 460 32. 1 105 440 150 Brt. stock 108 2, 050 11. 05 108 2,050

1 Single pass.

2 Recycle. Recycled as waxy lube oil prior to dewaxlng. Boiling 800-875 F.

From the data shown in Table III above it will be seen that the process of our invention is eifective to convert an undesired intermediate lubricating oil fraction, as exemplified by the 225 Neutral, into desired lubricating oil fractions. Furthermore, it will be noted that, as was also demonstrated in Example I, the process of our invention is effective not only to increase the quantity of desired lubricating oil fractions but also to enhance the quality of such fractions. Specifically, it will be noted that the yield of SAE 10 oil was increased from only 8 percent by volume up to 15.25 percent by volume when employing the recycle technique of our invention as opposed to the conventional single-pass operation. Moreover, this increase in yield of desired lubricating oil fractions is accompanied by a substantial increase in the viscosity index of such fractions as illustrated by the increase from 90 to 104 of the SAE 10 oil. Again, it will be noticed that the process of our invention is effective in increasing both the quantity and quality of desired lubricating oil fractions without significantly decreasing the overall yield of lubricating oils.

We claim:

1. A process for hydrotreating a crude lubricating oil stock to provide a lubricating oil having a desired yieldviscosity distribution and a desired viscosity index, which process comprises subjecting the crude lubricating oil stock to hydrotreatment at a temperature from about 600 to about 900 F., a pressure from about 1000 to about 5000 p.s.i.g., a liquid hourly space velocity from about 0.1 to about 10.0 volumes of total charge stock per hour per volume of catalyst, and a hydrogen feed rate from about 1000 to about 20,000 s.c.f./b. in the presence of a two-component catalyst comprising a hydrogenating component composited with a cracking base having an activity on the Kellogg scale of less than about 30, thereby producing on a nondewaxed basis at least about 50 percent by volume based on fresh crude lubricating oil stock of lubricating oil boiling above about 650 F. and containing lower viscosity components, selecting at least one fraction of the hydrotreated lubricating oil, which fraction boils above about 725 F. and has a viscosity greater than the viscosity of the lowest boiling components of the lubricating oil, and recycling at least a portion of the selected fraction to the hydrotreatment step in a recycle ratio of at least 10 percent by volume based on the fresh feed, thereby producing a total lubrieating oil product boiling above about 650 F. having an increased proportion of lower viscosity material and an increased viscosity index while producing a total of more than about 70 percent by volume based on the fresh crude lubricating oil stock of materials boiling above about 650 F.

2. The process of claim 1 wherein the hydrotreatment is conducted at a temperature from about 700 to about 800 F., a pressure from about 2000 to about 4000 p.s.i.g., a liquid hourly space velocity from about 0.5 to about 3.0 volumes of total charge stock per hour per volume of catalyst and a hydrogen feed rate from about 2000 to about 6000 s.c.f./b.

3. The process of claim 1 wherein'the selected fraction is recycled to the hydrotreating step at a rate from about 50 percent to about 600 percent by volume based on fresh crude lubricating oil stock.

4. The process of claim 3 wherein the recycle rate is at least 100 percent by volume.

5. The process of claim 1 wherein the lubricating oil boiling above 650 F. produced in the hydrotreatment step, on a nondewaxed basis, is at least about percent by volume based on fresh crude lubricating oil stock and the total production of materials boiling below about 650 F. is less than about 40 percent by volume based on the fresh crude lubricating oil stock.

References Cited UNITED STATES PATENTS 2,787,582 4/ 1957 Watkins et al. 208--58 3,078,238 2/ 1963 Beuther et a1. 208-264 3,142,634 7/ 1964 Ireland et al. 208- HERBERT LEVINE, Primary Examiner US. 01. X.R. 208-18, 264 -i 

